Myrmekiaphila Atkinson, 1886

BOND, JASON E. & PLATNICK, NORMAN I., 2007, A Taxonomic Review of the Trapdoor Spider Genus Myrmekiaphila (Araneae, Mygalomorphae, Cyrtaucheniidae), American Museum Novitates 3596 (1), pp. 1-32 : 5-9

Genus Myrmekiaphila Atkinson, 1886

Myrmekiaphila Atkinson, 1886: 131 (type species by monotypy Myrmekiaphila foliata Atkinson ).

Myrmeciophila: Simon, 1891: 316 (invalid emendation).

Myrmekiophila: Petrunkevitch, 1929: 516 (invalid emendation).

DIAGNOSIS: Males can be separated from those of the other euctenizine genera by the medially compressed and distally expanded metatarsus I (e.g., fig. 14, arrow). All species other than M. minuta (fig. 13) have a retrolateral ledge on the male palpal tibia (e.g., fig. 4, rl) and a subdistally serrated palpal bulb and embolus (figs. 24–32). Females have distinctive spermathecae that are strongly sclerotized (at least basally) and bear cuticular outgrowths at their base (e.g., fig. 39) and can be distinguished from those of all other euctenizines by the presence of the following combination of characters: preening combs on metatarsi III and IV, a rastellum borne on a prominent mound with small rastellar spines, and carapace uniformly sclerotized. These spiders are known only from the southeastern United States.

DESCRIPTION: Small to moderately sized trapdoor spiders, carapace 2.80–8.00 long, 2.25–6.81 wide, glabrous or lightly hirsute, with fringe of stout black bristles (3’s) or lacking setae. Carapace coloration ranging from yellowish-red to dark reddish-brown (figs. 2, 3). Abdominal coloration uniform dark reddish-brown dorsally (3’s) or some species with wide dusky stripes on dorsum (♀ ’s, fig. 3), ventrum and spinnerets pale yellow. Carapace sclerotization uniform across its entire length. Foveal groove generally deep, procurved; straight to slightly recurved in some species. Eyes either not elevated or in some species elevated slightly on low mound. AME, PME subequal in diameter in majority of species; AER slightly procurved, PER slightly recurved. Pars cephalica moderately elevated (not steep).

Sternum, as in most euctenizines, wider posteriorly, tapering anteriorly with widest point at coxae III. Posterior pair of sternal sigilla usually much larger, in some species nearly contiguous. Palpal endites longer than wide, small patch of few (3’s) or many (♀ ’s) cuspules concentrated on proximal, inner margin. Labium wider than long or subquadrate, with few or no cuspules. Anterior margin of chelicerae with 7–12 or more teeth, posterior margin with single row/patch of small denticles. Rastellum borne on distinct mound, armed with number of prominent spines. Anterior leg articles slender relative to posteri- or articles, lacking pseudosegmentation. Tarsi III, IV straight. Light to moderately dense scopulae on pedipalps (♀ ’s) and legs I, II; light scopulae on tarsus of legs III, IV in some species. Tarsi I with single row of trichobothria, usually arranged in zigzag pattern, sometimes interspersed with setae. Preening combs at tarsus-metatarsus joint on legs III, IV (♀ ’s), absent on leg III in some species.

Apical article of PLS digitiform, short; all three segments with fused spigots (see Bond and Opell, 2002: fig. 3H). Terminal segment with two or three enlarged spigots at tip. PMS single segment short, with spigots, terminus rounded.

Spermathecae relatively simple, comprising single pair of unbranched bulbs with moder- ately to heavily sclerotized base (e.g., figs. 39, 47). Distinctive male mating clasper (modified leg I, e.g., fig. 14); metatarsus medially compressed, expanded at metatarsus-tarsus junction. Cymbium of male pedipalp lacks spines, embolus with serrations or single tooth, some species with secondary prong (figs. 24–32).

DISTRIBUTION: Southeastern United States, extending westward into the Midwest and eastern Texas.

SPECIES GROUPS: We recognize three species groups for the purposes of facilitating identification. Because a phylogeny of the genus is not available at present, these informal groups are not intended to represent monophyletic taxa. The foliata group contains three species in which the male palp bears no second prong, having at most a single enlarged tooth or serration. The fluviatilis group contains six species in which the male palp bears a second prong. The minuta group comprises one species in which the male palp bears no second prong, having a vestige of a single embolar tooth situated distally rather than proximally, and lacking a retrolateral ledge on the palpal tibia. One species known only from females remains unplaced.

KEY TO MALES

1. Palpal tibia with retrolateral ledge (rl, fig. 4). 2

Palpal tibia without retrolateral ledge (fig. 102).................. M. minuta

2. Palpal bulb with embolus only, lacking accessory prong (figs. 4–6)............... 3

Palpal bulb with embolus and accessory prong (ap, figs. 7–12)................... 5

3. Distal dilation of metatarsus I small (fig. 15), palpal tibia usually short and robust, embolus lacking a prominent ledge (figs. 5, 25)....................... M. comstocki

Distal dilation of metatarsus I large (fig. 14).. 4

4. Embolus thick, with enlarged, retrolaterally directed subdistal tooth or ledge (figs. 4, 24); metatarsal dilation typically with more than

5.

6.

7.

8.

9. two ventral spines (fig. 35); palpal tibia generally slender (figs. 4, 36).... M. foliata

Embolus very thin, with or without enlarged subdistal tooth (if enlarged, tooth directed somewhat proximally, with wide angle between tooth and embolus); palpal tibia short (figs. 6, 26, 52)............. M. coreyi

Accessory prong much shorter than embolus (figs. 9, 29)...................... 6

Prong subequal in length to embolus (figs. 7, 27)............................ 9

Prong with accessory ledge below, appearing doubled distally (fig. 12, le)... M. howelli

Prong without such a ledge (fig. 7)....... 7

Prong typically ending in sharp point, tip pointing straight out or back up to embolus (fig. 9).................. M. torreya

Prong with thick, curved tip, with or without tooth before curve (figs. 10, 11)....... 8

Palpal tibia with retrolateral excavation, retrolateral ledge elongated and slender (fig. 10)............... M. neilyoungi

Palpal tibia without retrolateral excavation, retrolateral ledge short and stubby (fig. 11)................. M. millerae

Prong and embolus subequal, prong weakly curved; palpal tibia usually slender, with retrolateral ledge situated more proximally (fig. 8).................. M. jenkinsi

Prong slightly shorter than embolus, prong strongly curved; palpal tibia usually thicker, with retrolateral ledge situated distally (fig. 7)................. M. fluviatilis

THE FOLIATA GROUP